1. Field of the Invention
The present invention relates to an ultrasonic diagnostic apparatus that transmits ultrasonic waves to the inside of a patient's body to obtain tomographic images of the patient's body, and more particularly relates to an ultrasonic diagnostic apparatus that is provided with a head mounted display.
2. Description of the Related Art
An ultrasonic diagnostic apparatus has conventionally been used widely for diagnoses and examinations in the medical field. The ultrasonic diagnostic apparatus transmits ultrasonic waves to the inside of a patient's body, and generates ultrasonic tomographic images (hereinafter, referred to as the ultrasonic images) of the patient's body from the reflected echoes, and display them on a monitor. The ultrasonic diagnostic apparatus is basically constituted of an ultrasonic probe, a processor, and the like. The ultrasonic probe, which is used with being pressed against a surface of the patient's body, transmits the ultrasonic waves to the inside of the patient's body and receives the reflected echoes from the patient's body. The processor generates the ultrasonic image based on signals output from the ultrasonic probe according to the received echoes, and displays the generated ultrasonic image on the monitor.
The ultrasonic probe is formed to such a size that an operator like doctor or examination technician (ultrasonographer) can hold with one hand, and is connected to the processor wirelessly or through a flexible communication cable. Owing to this, the ultrasonic probe can be pressed against the patient's body while freely adjusting its position and angle. Meanwhile, the monitor on which the ultrasonic image is displayed is placed at a predetermined position like bed side with the processor. As the ultrasonic probe used apart from the monitor, the operator has to change the direction of gaze often between his hands to check the position and angle of the ultrasonic probe and the monitor to check the displayed diagnostic image during the diagnosis or examination using the ultrasonic diagnostic apparatus.
In order to remove the burden of often changing the direction of gaze, a head mounted display (FIND) which displays the ultrasonic image superimposed upon the operator's view observing the hand holding the ultrasonic probe has recently been known. Moreover, there is known a HMD which displays the ultrasonic image beyond the operator's line of sight by recognizing position of the operator's pupil (Japanese Patent Laid-Open Publication No. 2008-18015).
The commonly used ultrasonic probe (hereinafter, referred to as the 2D ultrasonic probe) has ultrasonic transducers arranged in a line, and obtains reception signals to be the tomographic images of the patient's body by transmitting and receiving the ultrasonic waves in a single plane. However, a 3D ultrasonic probe has recently been known. In the 3D ultrasonic probe, the ultrasonic transducers are two-dimensionally arranged, and transmits the ultrasonic waves to a three-dimensional area inside of the patient's body and receives the ultrasonic waves therefrom, thereby obtaining three-dimensional reception signals of this area (hereinafter, referred to as the 3D data). Breast cancer, for example, is said to be cured with a 90% chance of complete recovery if it is detected at an early stage (tumor thickness: 2 cm or less), and can be cured with a 100% chance of complete recovery if it is detected at a very early stage (tumor thickness: several millimeters). However, in inserting or puncturing a biopsy needle into such a small target, it is difficult to confirm whether the biopsy needle is accurately punctured into the tumor mass by observing the common 2D tomographic image. Therefore, the 3D ultrasonic probe is used in the recent breast cancer examination, and the biopsy needle is punctured while observing the ultrasonic images in a plurality of cross sections around the tumor mass.
Furthermore, there is known an ultrasonic diagnostic apparatus provided with the 3D ultrasonic probe and the HMD. In this apparatus, when the 3D ultrasonic image three-dimensionally representing the view inside of the patient's body is displayed on the HMD after obtaining the 3D data using the 3D ultrasonic probe, the 3D ultrasonic image seen from the direction of the operator's gaze is generated and/or displayed. Owing to this, operations related to the ultrasonic diagnostic apparatus can be reduced even when both of the operator's hands are occupied for the operations of the 3D ultrasonic probe and treatment tools (U.S. Pat. No. 6,416,476 corresponding to Japanese Patent Laid-Open Publication No. 2000-201925).
When the biopsy needle is punctured using the ultrasonic diagnostic apparatus, a relatively wide view of the ultrasonic image is generally observed in advance to check the position and number of the tumor, and to determine a site to be diagnosed. The above-described 3D ultrasonic image is useful for such wide view observation. In puncturing the biopsy needle, on the other hand, the planar ultrasonic image containing the biopsy needle is more useful as compared to the 3D ultrasonic image since an insertion path of the biopsy needle needs to be determined after carefully and precisely examining tissue characterization and the like of the site to be examined and its periphery. However, the conventional ultrasonic diagnostic apparatus provided with the 3D ultrasonic probe always displays the 3D ultrasonic image. To display the planar ultrasonic image (hereinafter, referred to as the 2D ultrasonic image) in arbitrary cross section of the patient's body, setting for generating or displaying the 2D ultrasonic image in which (what types of) cross section requires complex operations, and therefore the usability of the apparatus is not necessarily good.
In this way, when the 2D ultrasonic image is generated using the 3D ultrasonic probe, there may be a method to detect the operator's line of sight first, and to generate or display the 2D ultrasonic image of the cross section vertical to the line of sight with respect to the area for which the 3D data is obtained, like the U.S. Pat. No. 6,416,476 corresponding to the Japanese Patent Laid-Open Publication No. 2000-201925. Even in the case where the 2D ultrasonic image is generated using the 3D ultrasonic probe, however, the treatment tool such as the biopsy needle can easily be lost depending on a slight change of position or tilt of the ultrasonic probe, like the case of generating the 2D ultrasonic image with the conventional 2D ultrasonic probe. Moreover, since the cross section for which the 2D ultrasonic image is generated changes in response to the change of the operator's line of sight, the operator needs to fix not only the ultrasonic probe but also the head on which the HMD is mounted so as to observe the 2D ultrasonic image in a certain cross section, which causes burden to the operator. In view of this, in generating and displaying the 2D ultrasonic image using the 3D ultrasonic probe, it is more preferable to switch the ultrasonic image in appropriate cross section with simple operation as compared to changing the cross section in response to the change in the line of sight.